1. Field of the Invention
The present invention relates to the eradication of mosquitoes outdoors, especially close to dwellings or other buildings having humans or animals. The invention provides a system whereby the mosquitoes may be destroyed on a continual basis, where they gather, so that the insect population will decline.
It is the breeding female mosquitoes that are most active and which are attracted to humans and animals. By destroying these females the overall quantity of eggs laid within a specific area will be reduced and the overall number of mosquitoes will decline.
The invention makes use of the common knowledge that mosquitoes are attracted to heat and carbon dioxide. It is also known that these insects congregate at the lee side of buildings away from direct sunlight and wind. They will gather in the evening hours especially when the outside temperature drops below the temperature inside the building.
2. Prior Art
Many devices for killing mosquitoes outdoors are known. The majority of these use an electrically charged grid capable of killing mosquitoes which attempt to pass through the grid. The mosquitoes are attracted to the grid by various means, including canisters which produce carbon dioxide and/or special attractant chemicals, combustion of fuel which produces carbon dioxide, or by light, or heat. The use of these various attractants is discussed in the following patents:
U.S. Pat. No. 5,020,270, issued Jun. 4, 1991 to Lo;
U.S. Pat. No. 5,255,468, issued Oct. 26, 1993 to Cheshire, Jr.;
U.S. Pat. No. 5,301,458, issued Apr. 12, 1994 to Deyoreo, et al;
U.S. Pat. No. 5,595,018, issued Jan. 21, 1997 to Wilbanks;
U.S. Pat. No. 5,647,164, issued Jul. 15, 1997 to Yates;
U.S. Pat. No. 5,799,436, issued Sep. 1, 1998 to Nolen, et al.;
U.S. Pat. No. 6,050,025, issued Apr. 18, 2000 to Wilbanks, and
U.S. Pat. No. 6,055,766, issued May 2, 2000 to Nolen, et al.
Systems using canisters or fuel for providing carbon dioxide and/or other attractants have the disadvantage that the canisters or fuel need constant replenishment or replacement. The present invention provides apparatus which avoids this drawback, and which can operate for lengthy periods with nothing but a small supply of electricity.
Applicant is also aware of U.S. Pat. No. 6,305,122, issued Oct. 23, 2001 to Iwao, et al., which issue date is after Applicant""s priority date. The Iwao, et al. patent is different from the others in that, in addition to using chemical-type carbon dioxide generators of various kinds, it also suggests using carbon dioxide produced by humans or animals. Specifically, it includes a fourth embodiment shown in FIGS. 10 and 12 which uses carbon dioxide produced by dogs to kill mosquitoes in the neighbourhood of a dog house, and fifth and sixth embodiments shown respectively in FIGS. 12 to 14, and in FIGS. 15 and 16, which use carbon dioxide produced by human beings, along with heat produced by a heater, to attract the mosquitoes to the neighbourhood of a house. The fifth embodiment uses a sticky sheet to trap the mosquitoes, whereas the fourth and sixth embodiments use electric grids to kill the mosquitoes.
In the dog house version of the Iwao, et al. patent, the electric grid is in the ceiling of the dog house so that dead mosquitoes will fall inside the house. In the sixth embodiment, the grid is held vertically within a box structure installed in the wall of a house, so that dead mosquitoes will pile up inside this structure against the grid. No method of removing the mosquitoes is described; removal would seem to require some disassembly of the box structure. If not removed the dead mosquitoes would reduce the effective area of the grid.
The present invention avoids the need for canisters, fuel, etc., for supplying carbon dioxide by using the carbon dioxide produced by humans or animals inside a building, this carbon dioxide being ducted to mosquito killing apparatus which is located outside the building. Heat and moisture produced inside the building may also provide supplemental attractants. Unlike with the Iwao, et al. patent, the apparatus of this invention causes the dead mosquitoes to drop away easily from an electric grid and fall outside the building, and no special mosquito removal step is required.
In accordance with one aspect of the invention, apparatus for killing mosquitoes outdoors and in the neighbourhood of a building with an interior normally occupied by humans or animals, comprises:
exterminating means including an electrical grid, said means being suitable for mounting outdoors and adjacent said building and connectable to a supply of voltage, said grid separating an interior space from an atmosphere outside of the building, and being such that, when the grid is attached to a voltage supply, mosquitoes are killed on attempting to pass through the grid;
a duct for passing through a wall of the building and for connecting said interior space to the interior of the building,
the arrangement being such that air containing carbon dioxide produced by occupants of the building passes through the duct and into said interior space where it attracts mosquitoes to the grid for electrocution,
and wherein said grid is disposed above a relatively unobstructed space to allow mosquitoes to fall freely away from the grid and outside the building.
Generally, the grid is situated so that dead mosquitoes simply fall to the ground under the grid and outside the wall of the building. While the grid may be vertical, in preferred embodiments the grid is generally flat and either horizontal or sloping, in each case having its downwards side facing the outside atmosphere, so that dead mosquitoes may more easily fall off. If any container is used to collect the dead mosquitoes, this is spaced so that it does not cause mosquitoes to pile up against the grid, as would happen in the Iwao et al. patent.
The apparatus is mounted on an outside wall of a building, preferably on the lee side, with the duct passing through an opening in the wall to access the interior air. Preferably a fan, such as an in-line fan or duct fan, moves warm, moist air containing carbon dioxide from inside the building and through the duct into the interior space, which is inside the grid or adjacent the grid. The interior space may be inside an inner cylindrical grid of a standard kind of mosquito exterminating device sometimes termed an xe2x80x9cELECTRIC KILLING DEVICExe2x80x9d or EKD. Such devices usually have a light for attracting the mosquitoes, but this light is not needed with apparatus in accordance with this invention. The air passes out through the grid of the EKD into the atmosphere. Mosquitoes detect the warm, carbon dioxide containing air and follow the trail back to the EKD; as they try to locate the source of the air they strike the grid and are electrocuted. The dead insects fall out of the open bottom of the EKD to the ground or into a suitable container.
The use of a fan is a further distinction over the Iowa, et al. patent in which the corresponding sixth embodiment has no fan so that there would seem to be little movement of carbon dioxide to the outside where it can attract mosquitoes.
Preferably a screen is provided in the duct which prevents any mosquitoes entering the building even when the grid is not energized.
The invention also provides a method for killing mosquitoes, comprising conducting carbon dioxide containing air, produced by humans or animals inside a building, through a duct to the outside of the building, and supplying this air to an interior space separated from the outside atmosphere by an electrically charged grid, so as to attract mosquitoes to the grid where they are killed, and allowing the killed mosquitoes to fall away from the grid.